An acoustic wave resonator, such as a surface acoustic wave (SAW) resonator and a piezoelectric thin film resonator, is used as a filter excellent in a high frequency characteristic. With the spread of mobile communication terminals in recent years, a device which includes a plurality of filters, such as a demultiplexer and a dual filter, is used. In order to downsize the device, it is demanded that the plurality of filters are arranged close to each other. A substrate into which a plurality of SAW filters are embedded is described in Japanese Laid-open Patent Publication No. 2003-283139.
However, with the conventional technology, isolation between the filters might not fully be secured.